In the manufacture of integrated circuits, individual transistors are customarily interconnected with conductors, sometimes termed "runners."Interconnections are typically formed by processes which involve blanket depositing a layer of conductive material and then covering the conductive material with a photoresist. The photoresist is then usually exposed to light and (depending upon whether the photoresist is a "positive" or "negative" photoresist) either the exposed or the unexposed portion of the photoresist is washed away. The remaining photoresist covers a portion of the blanket conductive material, leaving other portions exposed. Next, the exposed conductive material is etched away by various means, leaving the desired conductive interconnections.
Aluminum is frequently used as a material for forming conductive interconnections in integrated circuits. A variety of aluminum etching techniques are in use. One example is found in U.S. Pat. No. 4,256,534 issued to Levinstein et al. The Levinstein et al. patent illustrates the etching of aluminum and aluminum-rich alloys by the use of halide- halogen combinations, such as e.g., boron trichloride and chlorine.
Another example of an aluminum etching technique is contained in: Arikado et al., "Al Tapered Etching Application to Submicron Multilevel Interconnection Process", IEDM pp. 54-57, 1986. The Arikado publication illusrates the use of chloroform together with chlorine to produce aluminum runners with tapered sidewalls. The tapered sidewalls are created in an effort to improve subsequent dielectric deposition.